1. Field of the Invention
The present invention relates to next generation wireless communication; and more particularly, to eliminating stall during the re-sequencing of received data packets.
2. Description of Related Art
In telecommunications systems, particularly next generation wireless packet data systems, a base station transmits data packets to user equipments. However, the user equipment does not necessarily receive the data packets in the same order as they were transmitted. This out-of-sequence problem is compounded in systems such as High Speed Downlink Packet Access (HSDPA) in which an in-band priority class indicator (PCI) has been proposed to differentiate between the priority of logical channels' multiplexed in the same transport channel. Namely, even though data packets of a given priority class are transmitted in order, data packets of the given priority class will be received out of order on the receive side. In addition, data packets of other priority classes will be received interspersed with the receipt of data packets for the given priority class.
It has also been proposed with HSDPA that an in-band transmission sequence number (TSN) be provided with data packets for the re-sequencing functionality on the received side. And, U.S. patent application Ser. No. unknown entitled “A MULTI-PRIORITY RE-SEQUENCING METHOD AND APPARATUS”, which is hereby incorporated by reference in its entirety, by the inventors of the subject application, discloses several methods of re-sequencing received data packets.
It is also the case that data packets are not received in certain types of systems. For example, when the receiver at a destination device (e.g., the user equipment) fails to decode a data packet, and sends the source device (e.g., the base station) of the data packet a non-acknowledge response indicating failure to properly receive the data packet, the source device is expected to retransmit the data packet. However, a transmission error (hereinafter “acknowledgement error”) can occur with the non-acknowledge response such that the source device interprets the response as an acknowledge response—indicating receipt of the data packet by the destination device. As a result, the source device does not retransmit the data packet, and a gap will exist in the sequence of data packets at the destination device. A gap in the sequence of data packets at the destination device is also created if a data packet of a lower priority class has its transmission aborted in favor of a data packet of a higher priority class.
U.S. patent application Ser. No. unknown entitled “A MULTI-PRIORITY RE-SEQUENCING METHOD AND APPARATUS” by the inventors of the subject application discloses using a timer or counter to flush gaps in the sequence of data packets. The delay in outputting data packets due to a missing packet is called a stall. The stall period is determined by the length of the timer, and is typically set for a worst-case transmission scenario. For example, it may take several re-transmission attempts for proper receipt of a data packet. The length of the count down timer can be set to permit a maximum number of these retransmission attempts. However, the acknowledgement error and data packet abortion scenarios described above occur very quickly—in much less time than the length of the count down timer. Consequently, a lengthy stall occurs.